Preventing fouling of metal conductors in a refinery process



Patented Oct. 1, 1963 3,105,810 PREVENTING FOULING F METAL CONDUC- TORSIN A REFINERY PROCESS Richard M. Miller, La Grange, and Harold I.Patzelt,

Chicago, Ill., assignors to Nalco Chemical (Iompany,

a corporation of Delaware No-Drawing. Filed Jan. 19, 1959, Ser- No.787,353

r 7 Claims. (Cl. 2084S) This invention relates to improvements in theintermediate refining stages of petroleum hydrocarbons. Specifically,the invention is concerned with chemical additives for normally liquidcharge stocks used to produce liquid and gaseous hydrocarbon fuels.

It is common practice to add chemical agents to finished petroleumhydrocarbon products such as gasolines,

kerosenes, 'fuel oils, finished solvents, and the like, to givethese-products desirable properties and characteristics. Modern refiningoperations use a large'number of charge stocks which are intermediatesin the production of finished petroleum products. Until recently littleattention was paid to the properties of these charge stocks since theywere rapidly processed through the refining equipment where they wereconverted to products having different physical and chemicalcharacteristics than those of the starting material.

With the ever-increasing need for higher octane gasolines, improvedaviation fuels and improved residual fuels, it has become the practiceto treat the various refinery charge stocks to extract improved fuelvalues therefrom. These various processes, while greatly improving thefuel yield of a given charge stock,.have tended to increase refiningproblems which, in the past, were not critical.

One of the worst-problems encountered in the treatment of variouspetroleum charge stocks is the phenomenon which is now recognized and isdescriptively called fouling. This phenomenon manifests itself in theform of deposits which frequently form on the metal surfaces of theprocessing equipment and tend to materially decrease the etficiency ofthe intermediate refining operations.- The direct results of foulingappear in the forms of heat transfer loss, increased pressure drops,loss in through-put and, in some instances, a specific type of corrosionproduct which is associated with the deposits.

The charge stocks which most commonly cause fouling in the intermediaterefinery equipment are naphthas, gas oils, and crudes. The naphthas orlight distillate stocks may be considered as a light oil, at least 10%of which boils below 347 F. and at least 95% distills below 464 F. Thegas oils which frequently are referred to as middle distillates usuallyare intermediates between the so-called kerosene fractions and the lightlubricating cuts. These gas oils are usually used as charges ,tocracking units where the molecules are broken down into smallercomponents. The crude oils which most commonly cause the problem offouling are virgin products charged to the first refining stageoperations and contain all of the petroleum fractions normally removedin the refining processes. For the purposes of this invention, crudestocks are intended to cover the so-called residual or pot'fractionswhich remain after the volatile components and solvent extractablecomponents of the crudes have been removed. a

The various charge stocks mentioned above are most frequently subjectedto one or more of the following general type processes to produce fuels:reforming, cracking,

7 changers, reboilers, and condensers.

alkylation, isomerization, polymerization, desulfurization,hydrogeneration, and dehydrogenation. These processes may be performedusing a number of specific refining techniques which frequently employcatalytic reagents. A description of these various processes and theirmodifications are described in the publication, Petroleum Refiner,September 1958.

The deposits previously mentioned most frequently occur at elevatedtemperatures which range between 200 F. and 1100 F. The types ofmechanical equipment most commonly affected are furnaces, heat ex- Inthese types of equipment, the charge stock is usually caused to flowthrough various types of heat processing equipment such as pipes, heatexchangers, furnaces, etccwhich, for purposes of simplification, arereferred to herein as conductors.

The deposits forming on the metal surfaces thus described are varied incomposition and may be either organic, inorganic, or mixed organic andinorganic, with the latter type deposit being the most common type foundin intermediate refining processes. The organic deposits are primarilypolymerization products and are usually black, gummy masses which may beconverted to coke-like masses at elevated temperatures. The inorganicportions of the deposits will frequently contain such components assilica, iron oxide, sulfur trioxide, iron sulfide, calcium oxide,magnesium oxide, inorganic chloride salts, sodium oxide, alumina, sodiumsulfate, copper oxides, and copper salts. The source of the inorganiccomponents of the deposits is difficult to locate in any one givenrefining operation, but frequently they may be ascribed as coming fromsuch sources as ash components of the crude oils, corrosion productsfrom the metal surfaces'the charge stocks contact, and contaminantsresulting from the contact with the various metallic catalytic reagentsused to process the stock.

ing are not readily solubilized by common organic solvents. Theinorganic deposits which occur as fouling products are frequently muchmore complex in their makeup than the conventional corrosion products;hence they are readily distinguishable on this basis.

When the fouling phenomenon first became apparent, it was believed itcould be corrected by using known anti oxidants or stabilizing chemicalsto mitigate the problem. The experience with these additives soondeveloped the fact that conventional petroleum additives were relativelyineffective. j i

It would be a valuable contribution to the art if the problems describedabove could be overcome byusing economical chemical additives atrelatively low dosages. This invention presents such a solution totheproblem.

' The invention in its simplest form comprises a petroleum refiningprocess for the production of liquid and formation of deposits on thesurfaces of the metalcon ductor. To prevent the formation of thesedeposits or fouling, the process is performed in the presence of achemical additive which is admixed with the charge stock. The chemicalscapable of preventing the fouling are oil soluble, alkarylsulfur-containing compounds, which contain a sulfonic acid radical.Compounds falling under this general category are the well-knownpetroleum sulfonic acids and alkyl benzene sulfonic acids and theirsalts of the general formula:

l o-si-o o In the above formula R is an alkyl radical from 8 to 22carbon atoms in chain length and x is an integer from 1 to 3. Theconstituent M will be explained more fully hereinafter.

The oil soluble petroleum sulfonic acid may be said to be those sulfonicacids having a molecular weight of at least 350-375. In a preferredembodiment of the invention the molecular weight of the sulfonatedtreating agent is in excess of 415, and may even exceed 1,000. Includedin the grouping of petroleum sulfonates are the well-known alkylsubstituted sulfonated naphthalenes.

As will be shown later, when the sulfonic acid grouping in the moleculehas been converted to the alkali metal salt form the sodium or potassiumsalts of a given acid will in most cases give results superior to thoseobtained when the free acid is used.

Due to the inherent corrosiveness of the free sulfonic acids, it isusually desirable from a handling standpoint to employ the reagents inthe form of their salts, which salts may be derived from a rather largenumber of anionic components. Thus, for instance, the amine salts may beused, as Well as the alkaline earth metal salts.

In some instances, particularly where the charge stock is a gas oilwhich is to be catalytically converted'using a silica-alumina typecatalyst such as, for instance, a fluidized catalyst used in a movingbed process, alkali metals tend to contaminate the catalyst; hence arenot too well suited for this type of operation. When such conditions arepresent, it is then expedient to use either the ammonia or amine saltsof the sulfonic acids which give satisfactory performance and do nothave the disadvantages of catalyst contamination. In referring back tothe formulas of the alkyl benzene sulfonic acid, the constituent M maythen be considered as being either hydrogen, alkali, alkaline earth, oran organic amine grouping. For purposes of illustrating severaloil-soluble alkaryl sulfur containing compounds, the Table I ispresented. Table IA lists several commercial stabilizers andanti-oxidants which will be compared to the compositions of theinvention in the examples.

TABLE I Composition Alkaryl S Compound Molecular Number Weight IPetroleum sullonie acid 405 IT do 400 III Sodium petroleum sulfonic acid415-430 Sodium dinonyl naphthalene sulfonate 482 Barium dinonylnaphthalene sulionate neu- 1055 tralized to basic pH. Barium dinonylnaphthalene sulionate new 1055 tral pH. Ethylene diamine petroleumsulfonate 505 Ethylefine diamine dinonyl naphthalene sul- 980 one e.Ethylene diamine salt of Composition I 490 Etihylezne diaminepolydodecyl benzene sul- 520 one e. Triethyl amine salt of Composition I500 Ammonium salt 01 Composition III 450 Ammonium dinonyl naphthalenesulfonate 417 The compositions are used at dosage ranges from as littleas one part per million to dosages ranging as high as 300 to 500 partsper million. The optimum treatment level which will work is dependentupon the type of charge stock, the type of intermediate refiningoperation to which the stock is subjected, and the temperature at whichthe particular process is performed. As a general rule, the dosage rangefor crudes will be between 5 parts per million and 300 parts permillion. In the case of naphthas, the dosage range will be between 10parts per million and 200 parts per million, with a preferred treatingrange being at between 5 and parts per million. When gas oils aretreated, the dosage may vary from 5 parts per million to 300 parts permillion, with optimum dosage levels being between 5 and 100 parts permillion.

One of the most interesting features of the invention is that theadditive remains preferentially with the liquid phase of the chargestock during the various refining stages. Thus, for instance, if a gasoil is subjected to a catalytic process, the additive does not carryover to any appreciable extent into the finished product, but willremain behind with the residual and non-converted components of theliquid or deposit itself on the surface of the reactor. In the case ofresidual fuels, the additive Will be carried over into the finished fuelproduct, but this is the only case wherein the additive will be found toany appreciable extent in a finished hydrocarbon product.

The additives may be added to the charge stock at any point in theprocess to be protected and will carry along with the production untilsuch a point in the refining operation where the product is convertedinto a different chemical component or species.

Thus, where a crude stock is passed through heat exchangers to a thermaldistillation unit to remove the lighter fractions, the additive may beadded just prior to the heat exchanger section of the operation and willafford protection to both the exchanger surface and other surfaces ofthe distillation or fractionation unit.

By indicating that the surfaces of the various units are protected, itis meant that the charge stock has been rendered non-fouling as to themetal surfaces; hence, deposit build-up does not occur. The process may,therefore, be considered as preventative rather than corrective in itsoperation. In some cases, the additives will remove existing fouling,but in most instances, the function of the additives is to preventfouling rather than remove existing deposits.

As indicated earlier, the components of the deposits will vary in theirchemical constituents and frequently contain a large number ofingredients. For purposes of greater understanding, Table II below ispresented to illustrate the types of deposits which the additives of theinvention tend to prevent.

Evaluation of the Invention The test apparatus used to evaluate refinerystream heat exchanger fouling and the effect ofthe anti-fouling proc- 6These standards are generally true in the case of gas oils and naphthasbut may be considered as toocri-tical for some crude stocks.

TABLE III 011 Wall HTO (U) at Percent Charge Cone. Duratmn Temp. Temp.Equil. End Percent Reduc- Oomp. No. Stock (p.p.m.) of Test at Equi-Equi- B.t.u./hr Reduction in (Hrs.) librium, librium Ft. F tion in UFouling F End, F. Rate A 5 I 443 725-802 94-74. 5 20. 7 A 5 449 699-727106-95 3 10. 2 49 A V 5 423 715-779 91-75 17.7 6 A 5 438 698-740 102-8813.9 26 A 5 454 699-741 108-93 14 5 A 5 437 698-747 101-86 14. 6 34 A 5456 703-756 107-90 17. 1 13 A 4. 5 411 717-808 97-75 23 A r 4. 5 428715-731 103-97 6. 2 69 "A 4. 5 436 730-754 100-94 7. 5 67 A 5 5 485801-872 87-72 18 A 5 473 786-800 89-86 3 83 A 5 475 790-802 90-85 5 72 A5 470 787-815 88-81 8 56 A 5 471 787-814 89-81 9. 50 A 5 473 792-82188-80 9 50 A' 5 480 808-819 85-83 3 A 5 509 800-805 110-109 1. 4 A 5 398708-799 88-69 21. 5 A 5 393 708-727 87-84 4 A 5 393 667-688 87-79 8. 4 A5. 5 529 834-856 108-104 4 A 5. 5 515 845-856 100-98 2 B 5 460 616-655180-139 23 B 5 469 622-650 183-156 14. 7 B 6 368 532-587 142-105 2 B 6381 535-548 153-138 B 4.5 489 754-787 84-74 12.4 398 546-670 91-51 43 05 393 535-564 95-88 8 3 D 8 564 637-676 273-217 25 D 8 566 663-663277-277 E 5 431 558-613 198-137. 32 E 5 442 566-566 203-203 0 E 5 440570-570 196-196 0 E 5 440 543-550 244-229 6 E 5 436 561-561 206-206 0ess consists of a variable injection pump, a recycle loop in which anelectrically heated heat exchanger tube is incorporated, and a variablerecycle pump in the loop.

The heat exchanger tube consists of an insulated resistance wire coilwound around a thick wall tube. The fluid being tested flows through thetube. The oil temperature at the outlet of the exchanger tube and thewall temperature of the tube are recorded continuously.

The fouling of the tube is determined by the change in heat transfercoefficient during the test after equilibrium has been attained. Thiscoefficient is determined from the following equation:

Q=UAAt where:

The results of the tests are reported in Table -III. To more completelyunderstand the results, the following general comparisons are presentedto clarify the percent reduction in fouling tabulations:

\ Percent Poor 20 Fair 20-50 Good -70 Excellent 70-100 5 Using thetreatment of the invention, the deposits when 2 present are usuallylight fluids which are readily removed using conventional cleaningtechniques. In all cases the depositsare materially lessened over theblanks.

The invention is claimed as follows:

50 1. Process for preventing fouling of a metal conductor through whichis passing material from the group consisting of naphthas, gas oils andcrude oils which are normally susceptible to the formation of foulingdeposits when passed through such metal conductor at 200-1100" F. forconversion of said material to an upgraded refinery product, whichcomprises adding to said material at least one part per million, basedon the Weight of said material, of an oil soluble alkaryl sulfurcontaining compound having a molecular weight of 350 to 1055 from thegroup consisting of petroleum sulfonic acids, their alkali, alkalineearth metal, and amine salts and alkyl benzene sulfonic acids andsulfonates of the formula o=s=o 0 l where R is an alkyl radical of from8 to 22 carbon atoms in chain length, x is an integer from 1 to 3, and Mis from the group consisting of hydrogen, alkali, alkaline earth metal,and amine, the amount of said oil soluble alkaryl Z sulfur-containingcompound being sufficient to reduce the formation of said deposits onthe surface of said metal conductor in contact with said material.

2. The process of claim 1 where the charge stock is a petroleumhydrocarbon liquid from the group consisting of crude oils, gas oils,and naphthas.

3. The process of claim 1 where the alkaryl sulfur compound is an alkalimetal salt of an oil-soluble petroleum sulfonic acid.

4. The process of claim 1 where the alkaryl sulfurcontaining compound isan alkali metal dodecyl benzene sulfonic acid containing from 1 to 3dodecyl radicals.

5. Process for preventing fouling of a metal conductor through which ispassing material from the group consisting of naphthas, gas oils andcrude oils which are normally susceptible to the formation of foulingdeposits when passed through such met-a1 conductor at 200-1100 F. forconversion of said material to an upgraded refinery product, whichcomprises adding to said material at least one part per million, basedon the weight of said material, of an oil soluble alkaryl sulfurcontaining compound having a molecular weight of 350 to 1055 and thefollowing chemical structure where R is an alkyl radical of from 8 to 22carbon atoms in chain length, x is an integer from 1 to 3, and M is from8 the group consisting of hydrogen, alkali, alkaline earth metal, andamine, the amount of said oil soluble alkaryl sulfur-containing compoundbeing suflicient to reduce the formation of said deposits on the surfaceof said metal conductor in contact with said material.

6. The process of claim 5 where the alkaryl sulfur compound is theethylene diarnine salt of an oil-soluble petroleum sulfonic acid.

7. The process of claim 5 where the alkaryl sulfurcontaining compound isthe ethylene diamine salt of a dodecyl benzene sulfonic acid whichcontains from 1 to 3 dodecyl groups per molecule.

References Cited in the file of this patent UNITED STATES PATENTS1,233,700 Petroff July 17, 1917 1,645,679 Axtell Oct. 18, 1927 2,261,206Archibauld Nov. 4, 1941 2,442,820 McCormick June 8, 1948 2,449,585 CampSept. 21, 1948 2,472,463 Brandon et al June 7, 1949 2,533,303 WatkinsDec. 12, 1950 2,626,207 Wies et al. Jan. 20, 1953 2,639,227 Glendenninget al May 19, 1953 2,845,393 Varvel July 29, 1958 2,908,624 Johnson eta1. Oct. 13, 1959 2,952,629 Schneider et al Sept. 13, 1960 FOREIGNPATENTS 951,303 France Apr. 11, 1949 OTHER REFERENCES Petroleum Refining=With Chemicals, Kalichevsky et -al., page 275, pub. Elsevier Pub. Co.,New York (1956).

1. PROCESS FOR PREVENTING FOULING OF A METAL CONDUCTOR THROUGH WHICH ISPASSING MATERIAL FROM THE GROUP CONSISTING OF NAPHTHAS, GAS OILS ANDCRUDE OILS WHICH ARE NORMALLY SUSCEPTIBLE TO THE FORMATION OF FOULINGDEPOSITS WHEN PASSED THROUGH SUCH METAL CONDUCTOR AT 200-1100* F. FORCONVERSION OF SAID MATERIAL TO AN UPGRADED REFINERY PRODUCT, WHICHCOMPRISES ADDING TO SAID MATERIAL AT LEAST ONE PART PER MILLION, BASEDON THE WEIGHT OF SAID MATERIAL, OF AN OIL SOLUBLE ALKARYL SULFURCONTAINING COMPOUND HAVING A MOLECULAR WEIGHT OF 350 TO 1055 FROM THEGROUP CONSISTING OF PETROLEUM SULFONIC ACIDS, THEIR ALKALI, ALKALINEEARTH METAL, AND AMINE SALTS AND ALKYL BENZENE SULFONIC ACIDS ANDSULFONATES OF THE FORMULA